Hydrocracking of a petroleum fraction containing nitrogen compounds with a nickel-tungsten catalyst on a silicamagnesia carrier



United States Patent HYDROCRACKING OF A PETROLEUM FRACTTUN CONTAINING NITRDGEN CUMPOUNDS WITH A NICKEL-TUNGSTEN CATALYST ON A SHHJA- MAGNESIA CARRIER Harold Beuther, Gibsonia, and Joel D. McKinney, Pittsburgh, Pa., Theodore Rice, Beaumont, Tex., and Bruce K. Schmid, Meredith MQStewart, and Eldon M. Sutphin, Pittsburgh, Pa, assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware N0 Drawing. Filed Apr. 25, 1963, Ser. No. 275,5112

10 Claims. (Cl. 208-410) This invention relates to the preparation of furnace oils, diesel fuels, jet fuels and similar middle oils by hydrocracking of heavier petroleum distillates.

It is well known that refined petroleum fractions can be hydrocracked to produce lower boiling hydrocarbons such as gasoline and/or jet fuels. This hydrocracking operation involves contacting the refinedhigher boiling fraction at elevated temperature and pressure with hydrogen in the presence of a hydrogenation catalyst such as palladium, nickel, etc. composited with a cracking base.

The cracking base customarily is a silica-alumina cracking catalyst. However, it has been indicated in many cases that silica-magnesia cracking type supports or carriers also may be employed. Actually, however, little or no data have been published on the use of such silica-magnesia supports. While the hydrocracking process is ordinarily directed toward the formation of relatively large amounts of hydrocarbons boiling in the gasoline range, in many cases some higher boiling materials such as middle oils, i.e., boiling above 250 F. and especially between about 400 and 650 F., are formed. In some cases this portion of the product has been recycled with unconverted feed stock. In other cases this portion of the product has been used as fuel oil, jet fuel, diesel fuel or the like. It is also known to convert heavier, unrefined hydrocarbons into gasoline and middle distillates using catalysts of the above mentioned type, but at relatively high pressures at which poisoning of the catalyst by impurities such as nitrogen compounds did not take place or took place at a relatively low rate.

This invention has for its object to provide a process whereby hydrocarbons which are relatively high in nitrogenous impurities and which boil above the furnace oil, diesel and jet fuel range can be converted in high yield into middle oil fractions, i.e., those boiling in the furnace oil, jet and diesel fuel range with relatively low concomitant conversion into gasoline. A still further object of this invention is to provide a relatively moderate pressure procedure for hydrocracking of higher boiling, im-

pure distillate feed stocks to obtain high yields of hydrocrackedproducts boiling in the 250 to 650 F. range and suitable for middle range fuels such as furnace oil, jet and diesel fuel or components thereof. Other objects will appear hereinafter.

These and other objects are accomplished by our invention which includes contacting a hydrocarbon boiling above furnace oil, diesel and jet fuels and containing a substantial amount of nitrogencompounds with hydrogen in the presence of a nickel-tungsten sulfided catalyst composited with a silica-magnesia cracking catalyst. This contacting takes place at a temperature between about 750 and 850 F. at a pressure between about 2000 and 3500 p.s.i., at a liquid hourly space velocity between about 0.2 and 10 and a hydrogen recycle rate of between about .2000 and 30,000 s.c.f./bbl. 'The specific reaction conditions employed are selected so that there is a conversion per pass of between about 40 and 65 percent of the feed, including recycle liquid when recycle is employed, into lower boiling products. We have found in accordance provide an economic process.

with our invention that this moderate pressure procedure results in an unusually high ratio of middle oil to gasoline and is therefore advantageous where large amounts of furnace oil, diesel fuel, jet fuel or the like are desired.

The feed stock employed in our process should boil above the desired products and preferably above about 650 F. It is preferably a petroleum distillate boiling with the range of between about 650 and 1100 F. For example, it may be a vacuum gas oil, heavy straight run gas oil, a heavy crackedgas oil, or any other vacuum or atmospheric distillate of petroleum distilling Within this range. Alternatively it may be a deasphalted residuum. Also it may be similar hydrocarbons derived from non-petroleum sources such as hydrogenated shale oil or coal. The feed stock may boil more or less uniformly over any portion of the range above 650 F. or may be one or more hydrocarbons or cuts boiling over a relatively narrow portion ofthis range. The feed may be predominantly aromatic, predominantly aliphatic, predominantly naphthenic, or mixtures of such different types of hydrocarbons. The feed is relatively unrefined and will usually contain above about 600 p.p.m. of nitrogenous compounds. However, it is essential thatit contain less than about 2 ppm. of vanadium and have a carbon residue below about 2 percent by weight, otherwise the throughput will be undesirably affected. As indicated, the product may be separated into the desired middle oils and gasoline and the higher boiling portion (usually that boiling above-650 'F.) recycled.

The hydrogen partial pressure employed in our process may be between about 2000 and 3500 p.s.i. It is advantageous for economic reasons to use as low a hydrogen partial pressure as possible consistent with long cycle length. Usually about three months cycle length before initial catalyst regeneration is theminimum which will Such a cycle length is easily obtainable with our operation. While pressures slightly below 2000 p.s.i. will, in certain cases, give satisfactory results in accordance with our invention, it is usually undesirable to use pressures below about 2000 p.s.i. since these pressures result in shorter onstream periods due to the relatively rapid deactivation of the catalyst by the relatively high carbon residue and/ or metal components present in many of the heavier feed stocks to which our invention is applicable. The relatively high nitrogen content of the feed stocks to which our invention is applicable also plays a partin this deactivation at pressures below 2000 p.s.i. Somewhat higher pressures than 3500 psi. may also be used. However, there are disadvantages in using pressures much above 3500 p.s.i., among which are the high cost of high pressure equipment. The hydrogen recycle rate may be between about 2000 and 30,000 s.c.f./bbl. and is preferably between about 5000 and 15,000 s.c.f./bbl. A space velocity (volumes of feed per volume of catalyst per hour) of between about 0.2 and 10 and preferably 0.5 to 4.0 may be used.

The temperature employed in our invention is maintained between about 750 and 850 F. during the main portion of the onstream cycle. However, slightly lower or higher temperatures may be used. Thus during the initial or start-up portion of the cycle a slightly lower temperature may be advantageous and a slightly higher temperature may be used toward the end of the cycle in order to maintain conversion and extend the length of the cycle. The temperature is initially adjusted to give a conversion of between about 40 and 65 percent, and the conversion is thereafter maintained in this range by increasing the temperature. Increasing the conversion above about 65 percent decreases the furnace oil-togasoline ratio, and use of below about 40 percent converfacture of such multi-component catalysts.

perature increase is necessary to maintain the desired conversion. When this point is reached the onstream reaction is terminated. The catalyst is then regenerated by combustion in the usual manner and thereafter re-used in the process.

The catalyst utilized in our process may contain between about 5 and 40 percent and preferably to 25 percent of nickel plus tungsten (determined as metals).

The atomic ratio may be between 1 atom of tungsten to 0.1 atom of nickel to 1 atom of tungsten to 5 atoms of nickel. We prefer a range of between 1 atom of tungsten to 0.3 atoms to 4 atoms of nickel. Any silica-magnesia carrier may be employed. Especially useful carriers have a surface acidity at 800 F. between 0.05 and 0.20 and contain between about 8 and 14 percent by weight magnesia, the balance being silica. A 60 to 95 percent magnesia, the balance between silica, having a surface acidity at 800 F. of between 0.05 and 0.15 in milliequivalents ammonia adsorbed per gram of support (see Barth et al., Analytical Chemistry, vol. 33, No. 8, pages 1080 to 1084 [July 1961]), is also an advantageous carrier. We have found that silica-magnesia carriers having the above mentioned specific magnesia contents give especially high ratios of the desired middle oils. However, magnesia contents of between 1 and 99 percent may be used. Any known method for preparing such silica-magnesia acidic compositions can be used. Thus they may be formed by coprecipitation from aqueous solutions of compounds containing silicon and magnesium. Alternatively they may be prepared by separate formation of a dry silica hydrogel and its impregnation with an aqueous solution of a magnesium salt followed by precipitation of magnesium hydroxide by means of ammonia. Since the preparation of these carriers does not constitute a part of our invention and is known in the prior art, this will not be described in greater detail. Reference is made to US. Patents 2,447,181, Aug. 17, 1948; 2,470,411, May 17, 1949; 2,611,738, Sept. 23, 1952; and 2,631,983, March 17, 1953 for further details on preparation of suitable silica-magnesia catalyst or catalyst carriers.

The final composite catalyst employed in our invention may be prepared using any known procedure for manu- Thus the nickel and tungsten components may be deposited in sequence on the silica-magnesia carrier with or without intervening drying and/or calcining. Simultaneous impregnation of the carrier from a two-component solution containing the two metals may also be employed. Thus the procedure described in McKinley et al. Patent 2,703,- 789 would be entirely satisfactory.

The hydrogena-ting components of these catalysts may be in the metal, oxide and/or sulfide states. In many cases it is preferable to use the components in the sulfide state and to introduce sulfur or sulfur compounds during processing. Thus although sulfiding somewhat deactivates the catalyst, it usually will become somewhat deactivated anyway by small amounts of sulfur usually found in these feed stocks. Also we have found that a superimposed activating effect is obtained when relatively high concentrations of sulfur or sulfur compounds are employed. If desired, the catalyst may be presulfided using any conventional sulfiding procedure but it is often more convenient and preferable if an unpresulfided catalyst is used initially and sulfided during use by sulfur compounds naturally present in or added to the feed. The presence of sulfur or sulfur compounds usually permits operation at lower pressures with good catalyst aging than would otherwise be possible. Of course with many feed stocks sulfur addition may not need to be practiced since they may contain up to 3 to 5 percent sulfur. If sulfur is to be added, it can be added to the fresh feed, recycle feed, make-up hydrogen and/ or recycle hydrogen gas streams. Especially suitable sulfur compounds for use are those having a hydrogen-to-sulfur or a carbon-tosulfur linkage such as butylmercaptan, thiophene, hydrogen sulfide, carbon disulfide, etc. Sulfur may be added so that contents in the feed, hydrogen, etc. based on total liquid hydrocarbon feed may vary from 40 p.p.m. to 2.0 percent. Larger amounts than 2.0 percent such as may be present in unpretreated feeds can be used but there does not appear to be any advantage in using them. Although we refer herein and in the claims to sulfides, sulfiding, etc., this is not to be taken necessarily to indicate the chemical form in which the hydrogenating components are present. Thus in accordance with our invention the hydrogenating components may be present as mixtures of the sulfides and/ or in the form of chemical combinations such as nickel thiotungstate.

It is advantageous, although unnecessary, to add a halogen, preferably fluorine, to the catalyst and/or the reacting mixture. Thus the halogen may be incorporated in the catalyst prior to use, may be injected into the reactor and/ or added to the hydrogen (for example, by means of suitable fluorine compounds such as difluoroethane,

orthofiuorotoluene, hydrogen fluoride, fluorine, etc.) The halogen may be combined with the catalyst during prep a-ration by means of a compound such as HF; NH F; NH F'HF, HgslFe or HBF or corresponding or similar compounds of chlorine or bromine, such as hydrochloric acid, etc. About 0.1 to 5 percent halogen may be combined with the catalyst as the result of prior addition or addition during the onstream period. We prefer to use a catalyst containing between 0.5 and 3.5 percent combined halogen and especially between 1.5 and 2.5. When adding halogen during the onstream period, the preferred halogen-containing compounds are the hydrogen halides and organic halides such as alkyl and aryl monohalides and polyhalides, halogen containing ketones, acids, aldehydes and the like. Preferred halogen addition agents are those having a relatively high halogen content such as carbon tetrachloride, carbon tetrafluoride, dichlorodifluoroethane, methylene iodide, bromoforrn and the like. The halogen is added to produce and/or maintain the combined halogen content of the catalyst within the pre: ferred limits. The amount added can vary widely de= pending on hydrocracking reaction conditions and upon whether the halogen is being added to bring the combined halogen content of the catalyst up to the desired level or to maintain the combined halogen content. Suitable levels of halogen addition are from 1 to 20 p.p.m. calcu lated as elemental halogen and based on total liquid reactor feed although there is usually no technical disadvantage of using a larger quantity. Addition can be continuous or intermittent. Often when operating to maintain the catalysts combined halogen content a very low rate of continuous addition or rather infrequent intermittent additions at a somewhat higher rate of addition is very adequate.

We include Within the scope of our invention the presence in the reactor of small amounts of water, i.e.,

'the hydrogen in any known manner. The separated hydrogen is at least partially recycled, usually after addition of make-up hydrogen and bleeding off part of the impure hydrogen to maintain hydrogen purity at between about 65 and percent. The liquid hydrocarbon prodnet is fractionated to separate the unconverted portion or that portion boiling above the desired product, i.e., furnace oil, diesel and/or jet fuel or the like. This higher boiling portion may be recycled. That portion of the product boiling between about 250 and 650- F. constitutes a high quality furnace oil, diesel or jet fuel or may be distilled to separate a fraction constituting a high quality middle oil product such as furnace oil, diesel and/ or jet fuels. The lowest boiling portion of the product is a high quality gasoline which is obtained in relatively low yields in accordance with our invention.

EXAMPLE A heavy vacuum gas oil having the properties given in Table I was hydrocracked on a single pass, using a catalyst consisting of 6 percent nickel and 20 percent tungsten (initially present as oxides) and 2 percent fluorine on a support containing 10 percent magnesia and 90 percent silica. The operating conditions were 800 F., 2000 p.s.i.g., 1.0 LHSV, and 10,000 s.c.f. of hydrogen per barrel of feed. The yield of gasoline (C 350 F.) was 11.7 percent by volume of charge while the 350 F.675 F. furnace oil yield was 43.9 percent (conversion to products boiling below 675 F. equalled 56 percent). This resulted in a ratio of furnace oil to gasoline of 3.75. In a similar run at the same conversion level, the ratio of furnace oil to gasoline is only 2.8 when using the same feed and a corresponding nickel-tungsten-fluor-ine catalyst made from a silica-magnesia support but containing about 30 percent magnesia. Therefore the 90 percent silicapercent magnesia catalyst is advantageous as com-pared with the 70 percent silica-30 percent magnesia catalyst where high furnace oil-to-gasoline ratios are desired. Similar tests show 10 percent silica-90 percent magnesia to be superior to the 70-30 percent catalyst. This 7030 percent catalyst is however superior, in regard to furnace oil-to-gasoline ratio, to the silica alumina cracking catalysts usually employed as carriers in hydrocracking. Thus a NiWF sulfided catalyst on 30 percent magnesia-70 percent SiO gave 14.8 percent gasoline and 41.3 percent furnace oil at 56 percent conversion while the same NiWF sulfided catalyst on Triple A silica alumina gave 18.6 percent gasoline and 37.3 percent furnace oil at the same conversion.

In the foregoing description and in the claims, in designating the pressure to be employed during hydrocracking we have at times referred to the hydrogen partial pressure while at other times it was found more convenient to refer only to the pressure. It is to be understood, however, that hydrogen partial pressure is intended to be designated when reference is made to the pressure used in the hydrocracking operation.

Table 1 PROPERTIES OF KUWAIT HEAVY VACUUM GAS OIL Gravity, API 20.7 Sulfur, percent by weight 3.2 Nitrogen, p.p.m. 970 Carbon residue, percent by weight 0.55 ASTM distillation (vac.), F.:

Over point 459 5% 698 10% 722 30% 799 50% 862 70% 919 90% 983 We claim:

1. A hydrocracking process for preparing a member of the group consisting of furnace oil, diesel oil, jet fuel and mixtures thereof with minimized formation of gasoline from a hydrocarbon feed stock which contains a substantial amount of nitrogenous compounds, which is relatively low in content of vanadium, which has a relatively low carbon residue, and which boils substantially above about 650 E, which process comprises contacting said hydrocarbon feed stock with hydrogen in the presence of a nickel-tungsten catalyst composited with a silica-magnesia carrier, at a temperature between about 750 and 850 F., at a hydrogen partial pressure between about 2000 and 3500 p.s.i., at a space velocity between about 0.2 and 10.0, at a hydogen ratio of between about 2000 and 30,000 s.c.f./bbl. and at a conversion 6 into lower boiling products of between about 40 and 65 percent.

2. A hydrocracking process for preparing a member of the group consisting of furnace oil, diesel oil, jet fuel and mixtures thereof with minimized formation of gasoline from a hydrocarbon feed stock which contains above about 600 p.p.m. of nitrogenous compounds, which contains less than 2 p.p.m. vanadium, which has a carbon residue below 2 percent by weight, and which has a 5 percent point above about 675 R, which process comprises contacting said hydrocarbon feed stock with hydrogen in the presence of a nickel-tungsten sulfide catalyst composited with a silicaqnagnesia carrier, at a temperature between about 750 and 850 F., at a hydrogen partial pressure between about 2000 and 3500 p.s.i., at a space velocity between about 0.2 and 10.0, at a hydrogen ratio of between about 2000 and 30,000 s.c.f./bbl. and at a conversion into lower boiling products of between about 40 and 65 percent.

3. A hydrocracking process for preparing a member of the group consisting of furnace oil, diesel oil, jet fuel and mixtures thereof with minimized formation of gasoline from a petroleum fraction which contains above about 600 p.p.m. of nitrogenous compounds, which contains less than 2 p.p.m. of vanadium, which has a carbon residue below 2 percent by weight, and which has a 5 percent point above about 675 F. which comprises contacting this fraction with hydrogen in the presence of a nickeltungsten sulfide catalyst composited with a silica-magnesia carrier, at a temperature between about 750 and 850 F., at a pressure between about 2000 and 3500 p.s.i., at a space velocity between about 0.2 and 10.0, at a hydrogen ratio of between about 2000 and 30,000 s.c.f./b'ol. and at a conversion into products boiling below about 675 F. of between about 40 and 65 percent.

4. A hydrocracking process for preparing a member of the group consisting of furnace oil, diesel oil, jet fuel and mixtures thereof with minimized formation of gasoline from a petroleum fraction which contains above about 600 p.p.m. of nitrogenous compounds, which contains less than 2 p.p.m. of vanadium, which has a carbon residue below 2 percent by weight, and which has a 5 percent point above about 675 F. which comprises contacting this fraction with hydrogen in the presence of a nickel-tungsten catalyst composited with a silica-magnesia carrier, which contains between about 60 and percent magnesia, at a temperature between about 750 and 850 F., at a pressure between about 2000 and 3500 p.s.i., at a space velocity between about 0.2 and 10.0, at a hydrogen ratio of between about 2000 and 30,000 s.c.f./bbl. and at a conversion into products boiling below about 675 F. of between about 40 and 65 percent.

5. A hydrocracking process for preparing a member of the group consisting of furnace oil, diesel oil, jet fuel and mixtures thereof with minimized formation of gasoline from a petroleum fraction which contains above about 600 p.p.m. of nitrogenous compounds, which contains less than 2 p.p.m. of vanadium, which has a carbon residue below 2 percent by weight, and which has a 5 percent point above about 675 F. which comprises contacting this fraction with hydrogen in the presence of a nickeltungsten catalyst composited with a silica-magnesia carrier which contains between about 8 and 14 percent magnesia, at a temperature between about 750 and 850 F., at a pressure between about 2000 and 3500 p.s.i., at a space velocity between about 0.2 and 10.0, at a hydrogen ratio of between about 2000 and 30,000 s.c.f./bbl. and at a conversion into products boiling below about 675 F. of between about 40 and 65 percent 6. A hydrocracking process for preparing a member of the group consisting of furnace oil, diesel oil, jet fuel and mixtures thereof with minimized formation of gaso line from a petroleum fraction which contains above about 600 p.p.m. of nitrogenous compounds, which contains less than 2 p.p.m. of vanadium, which has a carbon residue below 2 percent by weight, and which has a 5 percent point above about 675 P. which comprises contacting this fraction with hydrogen in the presence of a nickel-tungsten catalyst composited with a silica-magnesia carrier, at a temperature between about 750 and 850 F., at a pressure between about 2000 and 3500 p.s.i., at a space velocity between about 0.2 and 10.0, at a hydrogen ratio of between about 2000 and 30,000 s.c.f./bb1. and at a conversion into products boiling below about 675 F. of between about 40 and 65 percent, separating the product into components boiling below and above about 675 F., recycling the components boiling above about 675 F. and maintaining sulfur compounds at about 40 p.p.m. to 2.0 percent of total liquid hydrocarbon feed.

7. The process of claim 6 in which 1 to 20 p.p.m. of halogen and 5 p.p.m. to 1.0 percent water (based on total liquid feed) are present during the process.

8. The process of claim 6 in which 1 to 20 p.p.m. of

halogen (based on total liquid feed) is present during the process.

9. The process of claim 6 in which 5 p.p.m. to 1.0 percent water (based on the total liquid feed) is present during the process.

10. The process of claim 6 in which the catalyst contains from about 0.1 to about 5.0 percent by weight of combined halogen (based on the total catalyst).

References Cited by the Examiner UNITED STATES PATENTS 2,934,492 4/1960 Hemrninger et a1. 208-112 5 2,956,002 10/1960 Folkins 208110 3,058,906 10/1962 Stine et a1. 208-111 3,078,221 2/1963 Beuther et a1. 208111 DELBERT E. GANTZ, Primary Examiner.

vALPHONSO D. SULLIVAN, Examiner. 

1. A HYDROCRACKING PROCESS FOR PREPARING A MEMBER OF THE GROUP CONSISTING OF FURANCE OIL, DIESEL OIL, JET FUEL AND MIXTURES THEREOF WITH MINIMIZED FORMATION OF GASOING FROM A HYDROCARBON FEED STOCK WHICH CONTAINS A SUBSTANTIAL AMOUNT OF NITROGENOUS COMPOUNDS, WHICH IS RELATIVELY LOW IN CONTENT OF VANADIUM, WHICH HAS A RELATIVELY LOW CARBON RESIDUE, AND WHICH BOILS SUBSTANTIALLY ABOVE ABOUT 650*F., WHICH PROCESS COMPRISING CONTACTING SAID HYDROCARBON FEED STOCK WITH HYDROGEN IN THE PRESENCE OF A NICKEL-TUNGSTEN CATALYST COMPOSITED WITH A SILICA-MAGNESIA CARRIER, AT A TEMPERATURE BETWEEN ABOUT 750* AND 850*F., AT A HYDROGEN PARTIAL PRESSURE BETWEEN ABOUT 2000 AND 3500 P.S.I., AT A SPACE VELOCITY BETWEEN ABOUT 0.2 AND 10.0, AT A HYDROGEN RATIO OF BETWEEN ABOUT 2000 AND 30,000 S.C.F./BBL. AND AT A CONVERSION INTO LOWER BOILING PRODUCTS OF BETWEEN ABOUT 40 AND 65 PERCENT. 